The present invention relates to a protection device for a horizontal scanning control of a display screen and particularly a device for a cathode-ray screen for use in a terminal, which generates all the sync signals necessary for the display of a picture or image on the screen. Thus, the sync signals are generated as soon as the terminal is made live.
In the case of this type of screen, the horizontal scanning control is supplied by means of a transistor, which receives the sync signal at its base. However, when turning on or off, the sync signal is not stable and consequently the scanning control transistor requires protection, because it can be subject to high voltage or current variations, which may lead to the deterioration thereof. This draw back is usually prevented by the use of an integrated oscillating circuit, whose inherent oscillating frequency is roughly equal to the line frequency. Thus, this circuit makes it possible to continuously have a very stable scanning sync signal, so that there is no need for the transistor to have a special protection. The main disadvantage of this method is the high cost of this type of oscillator and the auxiliary circuits which it requires.